Traditional aircraft components have been built as single function units that include all of the elements of a specific system. Each such component can be removed as an integral unit for maintenance and replaced with a spare while the maintenance is being done. For this reason, these components are often called “line replaceable units” (LRUs).
Further, vendors design these LRUs to be completely proprietary, since each LRU is intended to only accept cards designed and provided by the vendor that produced it. The backplanes in LRUs contain custom traces or leads that carry vendor proprietary unit and electronic card controls and communications for which the interface specifications are often not publicly available and can only be purchased or licensed from the vendor.
In all such units, the backplane includes leads or traces that carry power to individual slots in the LRU, such that when a card is plugged into the backplane, it obtains power from it. These devices are designed to provide adequate power and cooling to all available card slots, regardless of whether all of the card slots are actually populated with cards.
The design of these systems is often completed years before they are installed in an aircraft, and they are intended to remain untouched or unmodified for additional years. However, as the development of computer processors, memory, storage, and related electronic component technologies continues to progress over time, the available processing power increases, memory capacity increases, and the physical size of storage decreases. In addition, the power consumption and heat generation of these new and more powerful components tends to decrease based on improvements in IC technology. Thus, computers become smaller, faster, more capable, cooler, and require less power to operate. However, the older design of LRUs cannot readily be updated to take advantage of such improved components.
A further complicating factor for the aircraft system vendors is that components that were used in an older design for processing and memory storage cards may no longer be commercially available several years after an LRU was originally installed, when the aircraft owner might want to add one or more other cards to the unit. Because of the proprietary nature of the LRU, it may not be possible for a third party to provide a card that can simply be added to the LRU. The only current solution is to have the system vendor that provided the LRU, design proprietary new cards at a considerable expense to the airline. Often, the design of the overall system or unit precludes the support or addition of desirable common features, like network, wireless, remote monitoring and diagnosis, etc.
In addition, adding a new card with new electronic components or system functions to an existing avionics unit requires the entire system to be re-certified by the FAA for use on an aircraft, since any new electronic components or functions may generate new interactions with the existing cards through their common connections on the backplane of the avionics unit.
Accordingly, it would be desirable to provide an alternative approach for adding cards with additional desired functionality to existing LRUs or for replacing original cards with new cards that use improved components and which operate faster or more efficiently than the original cards—without the need to obtain a new card from the original vendor of the LRU and without the need to purchase a license from the vendor to enable a third party to provide the new card, or to obtain FAA re-certification of the existing cards and unit functionality. It would further be desirable to use the existing power and cooling provided by an LRU for improved replacement cards or new cards added to empty slots in the LRU, where the new cards provide new or improved functionality and do not require a proprietary license to build and operate. Such an alternative approach should enable an aircraft owner to use existing systems on their aircraft that have unused slots to add new non-proprietary functionality or to upgrade existing cards, and to provide support for new system functions or features with enhanced processing power, memory, storage, networks, and other benefits.